r: Refresh view

a: Add a new subscription

/: Search (moves the cursor to the search box)

j/k: Select the next item in the list. You can use this to rapidly scan through a feed.

Space/shift-space: Page down/up, which enables you to scan through longer articles and posts easily.

Shift-n/shift-p: Select the next/previous feed in the list of feeds.

Shift-o: Open selected feed.

m: Mark current item read (or unread).

Shift-a: Mark all items in the current feed as read. This is handy when you subscribe to as many feeds as I do and are constantly confronted by over 1,000 unread items.

v: View original. This is useful for jumping to the web site or blog the item comes from. Note that this opens the original site in a new window, which your popup blocker may disallow.

I forget these too easily and default to lame mouse behavior, and every time I re-discover them I'm amazed at how quickly they allow you to fly around GR.